Getter and the application thereof



Patented Apr. 5, 1927. 1

- UNITED STATES iPA TE NT oFFicE.

DUNCAN MACRAE, 0F EAsToEANGE, AND HENRY KNEELAND RICHARDSON, OF NEW-ARK, NEW JERSEY, ASSIGNORS T0 WESTINGHOUSE LAMP COMPANY, A coEPoEa- TIONOF PENNSYLVANIA.

GETTER AND THE APPLICQTIQN. THEREOF.

No Drawing. Application filed June 8,

This invention relates to electrical devices comprising filamentsadapted to be heated to incandescence and more particularly tosubstances to be applied to such filaments to increase the efficiencythereof.

An object of our invention is the provision of a method for causinggetter-s or other beneficial substances to adhere to the filaments forelectrical, devices in a proper and efficient manner without using-anorganic binder.

Another object of our invention is the provision of an improvedsubstance for increasing the efficiency of incandescent lamps and otherelectricaldevices comprising incandescent filaments."

A'further object of our invention is the provision of a fusible getteror the like con: tainingan infusible or refractory admixture thereto,for the purposeof causing an even distribution of the getter on afilament and.

preventing the formation of fused beads of the getter substance on thefilament.

A still further object of our invention is thepreparation of a getter orthe like comprising a refractor or infusible substance admixed with afusi le substance adapted to cause the refractory portion of the getterto adhere closely to an incandescent filament when the same is heatedafter the getter is applied thereto. Other objects and advantages willbeapparent as the description proceeds.

In the copending application Serial No. I'TQLG'PZ. MmRae, filed May 18'.1921, a getterand method of applying the same, and

assignedto the Westinghouse Lamp Com- 7 pany, thereis described a methodof applying a getter consisting of cryolite which comprises fusing it toa filament for an incandescent lamp or the like. This method would beinapplicable to substance'ssuch as thoria, alumina, or other refractorymaterials which it might be desired to apply to a filament, be-

cause such substances cannot be fused conveniently in practice and,therefore, if used alone cannot b'e'made. to adhere to'thefilament. 1 4I I Our invention obviates the above noted difficulty by providing agetter composed primarily of twoconstituents or classes of constituents.One constituent or class of constituent-s is'rcfractory or infusible andmay comprise thoria, CGIIUID'QXldG, yttrium oxide, alumlna, silica oramlxture of two or more of 1922. Serial No.-566,847.

not be rubbed off during any of the usual.

manufacturing operations.

Our invention also contemplates a method of firmly affixing the getterto one or more of the parts of a lamp without the use of an organicbinding material. It also aims to provide a method of introducing agetter .into a lamp in a manner whereby the same is substant ally freefrom adsorbed gases. By

eliminating organic material and adsorbed gases, the prese'ntinventionremoves the necessity of providing a substance, such as phosphorus, tocombine with such gases. v

It has been found that the small amount of residual gas in a lamp afterexhaustion may be efficiently disposed of by our getter which is alsointroduced to off-set the obscuring effect of volat-ilized filamentarymaterial. Many kinds of material'may be used in preparing a getteraccording to our inven-. tion, the requirements of our getter being thatthe materials used shall be beneficial to the lamp. and that part of thegetter shall be refractory or infusible and another part shall be moreor less fusible. Although we have mentioned certain substances which weprefer to use in preparing our getter, it is to be understood that thesame are merely illustr'ative and we are not restricted to their use.

thoria and cr'yolite in desired proportions,

such, for example, as two parts of tho'ria and one part of cryolite, ispreferably powdered and mixedwith a liquid medium, such as water, toform' a solution or suspension mixture, and is preferably applied to thefilamentary material before the latter is mounted on the stem of a lamp.The filamentary material is furnace and-there the coating becomes heateda amount of getter applied is a'predeterminedto a temperature highenough'to dry'fdehydrate and melt the fusible constituent orconstituents, in this instance, cryolite. If the filament is composed oftungsten or other substance which readily oxidizes when heated, thecoating should be fused thereon in an atmosphere of hydrogen or othernon-oxidizing gas. This process causes the getter to become firmlyaffixed to the filamentary ma terial and atthe same time, expelsadsorbed gases and reduces the surface area of the getter material torender it less adsorbent to gases. s

It has been found'that a fused coating of getter strengthens a filament,such as tungsten, so that the latter may be more readily handled withoutbreaking. This additional strength is especially valuable in filamentsof r very small diameter, as such break very easily.

The filamentary material or wire when it has fused thereon a coating ofgetter, may be mounted on a spider for an incandescent lamp in the usualmanner. After sealing the mountso formed in a. bulb and the evacuationand tipping off of the same, the lamp may be lighted at its designedpotential or normal voltage without the necessity of auxiliaryapparatus. to guard against short circuits therein, inasmuch as there isnot present a sufiicient quantity of gases to ermit gaseous conductionon lamp voltages. lVhen the lamp is lighted, the incandescent filamentserves to vaporize a portion of the getter which, in such state,combines withthe small amount of residual gas, chemically or physically,and, reaching the comparatively cool surfaces of the bulb, is condensedas an invisible deposit and there serves the purpose of adsorbing theordinarily obscuring deposit of filamentary material which otherwisewould cause blackening of the bulb.

The thoria, in the getter previously described in detail, may bereplaced, in whole or in part, by cerium oxide, yttrium oxide, aluminaor other similar refractory substances. The cryolite in the getter maybe replaced, wholly or partly, by lithium.

fluoride, boric oxide, orsimilar fusible substances. Experience hasshown, that a filament coated according to the present invention willresist the ordinary abrasion which may occur in manufacturingmanipulations and retain such coating on the wire in substantially thefull quantity applied. This is a distinct advantage, inasmuch as thequantity calculated for the greatest efliciency of the lamp.

The present invention is also applicable to the manufacture of vacuum orgas-filled tubes, which employ an electronemitting element. Suchelements of electron tubes may consist ofan electrode coated withmaterials, such as oxides, which function as the primaryelectron-emitting element. ,It is desirable that the electron emissionfrom such coated electrodes be constant in quantity, which requires thatthe coating he retained on the electrode'without loss therefrom. Themethod disclosed in the present invention of firmly affixing such arefractory coating to an electrode will, therefore, be valuable in themanufacture of electron tubes.

WVhile we have described what we now consider preferred means ofpracticing our invention, itis to be understood that man changes may bemade therein within the spirit and scope of the appended claims.

What is claimed is: v 1. The method of treating incandescent lampfilaments comprising applying a refractory getter thereto by means of aninorganic binder fused to the filament, introducing the filament into abulb, exhausting the bulb, vaporizing the binder and thereaftervaporizing the refractory getter.

2. A filament for an incandescent lamp or the like evenly coated with afirmly adherent film comprising a refractory getter substance and aninorganic fusible substance the latter of which is fused onto thefilament.

3. In an electric device comprising an evacuated sealed envelope, afilament having a firmly adherent coating consisting of a mixture of aninfusible getter substance and a. fusible substance the latter of whichis fused onto the filament.

4. In an electric device a metallic filament comprising a firmlyadherent coating of a mixture ofthoria and cryolite adapted to be raisedto incandescence by the initial application of normal voltage.

5. In an electric device comprising an evacuated sealed envelope, ametallic filament having fused thereon a uniform coatingof a powderedmixture of thoria and cryolite.

In testimony whereof, we have hereunto subscribed our names this 7th dayof June,

DUNCAN MacRAE.

HENRY KNEELAND RICHARDSON.

